Multi-cylinder internal combustion engine with a system for variable actuation of the intake valves and an injector housing having a raised sealing edge

ABSTRACT

In a multi-cylinder internal combustion engine, provided with a system for variable actuation of the intake valves of the engine, the fuel injector associated to each engine cylinder is surrounded by a sealing casing which is part of a support body. The support body is mounted on the engine cylinder head with the interposition of a support surmounting the head and defining the seat in which the camshaft is received and it defines a sealing peripheral edge cooperating with a sealing cover which is mounted on the cylinder head. The cover has a general base plane sealingly mounted on the cylinder head or on the support. The sealing peripheral edge of each sealing casing is arranged in a parallel plane and raised with respect to the general base plane of the cover.

The present invention refers to internal combustion engines of the typeprovided with a system for variable actuation of the intake valves ofthe engine.

Even more particularly, the invention refers to multi-cylinder internalcombustion engines which comprise, for each cylinder:

a fuel injector,

at least one intake valve and at least one exhaust valve each providedwith respective return spring means which push the valve towards aclosed position, for controlling respective intake and exhaust conduits,

at least one camshaft, for actuating the intake valves of the enginecylinders by means of respective tappets,

wherein each intake valve is controlled by the respective tappet,against the action of the aforementioned return spring means, byinterposing hydraulic means including a pressurised fluid chamber and ahydraulic actuator associated to each intake valve and connected to saidpressurised fluid chamber,

said pressurised fluid chamber being adapted to be connected by means ofa solenoid valve with an exhaust channel with the aim of decoupling theintake valve from the respective tappet and causing the quick closure ofthe valve due to the respective return spring means,

said hydraulic actuator further being provided with hydraulic brakingmeans for slowing the final phase of the travel for closing the intakevalve controlled thereby when the pressure chamber is connected to theexhaust channel,

electronic control means for controlling each solenoid valve so as tovary the opening and/or closing and/or lift instants of the respectiveintake valve as a function of one or more engine operative parameters,

wherein the hydraulic means for controlling the intake valves of theengine and the solenoid valves associated thereto are part of apreassembled unit mounted on the engine cylinder head.

An engine of the type indicated above is for example described andillustrated in EP 1 338 764 A1 of the applicant.

Over the years, the Applicant has developed internal combustion enginescomprising a system for variable actuation of the intake valves of thetype indicated above, sold under the trademark “MULTIAIR”. The Applicantowns various patents and patent applications regarding engines providedwith a system of the type described above.

According to what is indicated in the document EP 1 338 764 A1 theentire unit for the variable actuation of the intake valves of theengine is integrated in a single “brick” which can be easily alsoadapted on an engine initially designed without the system for variableactuation of the intake valves.

SUMMARY OF THE INVENTION

The object of the present invention is that of improving theabovementioned known system, with particular reference to the simplicityof construction and assembly as well as reducing the overall dimensions.One specific problem requiring to be solved in an engine of the type inquestion lies in providing a sealing casing around each injector of theengine in the limited space available adjacent to each cylinder, due tothe presence of the actuators of the intake valves of the engine.

With the aim of attaining such objects, the invention has the object ofproviding an engine having the characteristics indicated above andfurther characterised in that the fuel injector associated to eachengine cylinder is surrounded by a sealing casing which is part of asupport body mounted on the engine cylinder head. such casing defines asealing peripheral edge cooperating with a sealing cover which ismounted on the cylinder head, and having a general base plane sealinglymounted on the cylinder head. The sealing peripheral edge of eachsealing casing is arranged in a plane parallel and raised with respectto the general base plane of said cover.

Due to the aforementioned characteristics, the sealing around eachinjector is suitably guaranteed, regardless of the presence—closelyadjacent to the injector—of the components of the intake valvesactuation system.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will be apparentfrom the description which follows with reference to the attacheddrawings, provided by way of non-limiting example, wherein:

FIG. 1 is a sectional view of an engine according to the known art, ofthe type described for example in document EP A 0 803 642 of theapplicant,

FIG. 2 is a partial perspective view of the cylinder head of a dieselengine according to a first embodiment of the present invention,

FIG. 3A is a perspective view, partially transparent, of a singlesub-unit for the variable actuation of the intake valves associated toan engine cylinder of FIG. 2,

FIG. 3B is a further perspective view of the support body of thesub-unit of FIG. 3A,

FIGS. 4, 5 are sectional views showing the detail of a bracket forlocking an injector of the engine of FIG. 2,

FIG. 6 is a perspective view of a cover associated to the cylinder headof FIG. 2,

FIG. 7 is a capsized perspective view of the cover of FIG. 6,

FIG. 8 is a bottom view of the cover of FIG. 6,

FIG. 8A is still a perspective view of a single sub-unit for actuatingthe intake valves associated to an engine cylinder,

FIG. 8B is a sectional view of the sub-unit of the FIG. 8A,

FIG. 9 is a perspective view of a unit associated to the cylinder headof a further embodiment of a diesel engine provided with a system forvariable actuation of the intake valves of the engine, which also formspart of the present invention,

FIG. 10 is an enlarged scale perspective view of a component of the unitof FIG. 9,

FIG. 11 is a sectional view of the unit of FIG. 9, and

FIG. 12 is a perspective view of a bracket for locking an injector ofthe engine on which the unit of FIG. 9 is mounted.

DETAILED DESCRIPTION OF THE INVENTION

Over the years, the applicant has developed internal combustion engines,petrol or diesel-fuelled, comprising a system for variable actuation ofthe intake valves of the engine, sold under the trademark “MULTIAIR”.The Applicant owns various patents and patent applications regardingengines provided with a system of the type described above.

FIG. 1 of the attached drawings shows a sectional view of apetrol-fuelled engine provided with “MULTIAIR” system, as described inthe European patent EP 0 803 642 B1 of the applicant.

With reference to FIG. 1, the engine illustrated therein ismulti-cylinder engine, for example an engine with four in-linecylinders, comprising a cylinder head 1. The head 1 comprises, for eachcylinder, a cavity 2 formed by the base surface 3 of the head 1,defining the combustion chamber, in which the two intake conduits 4, 5and two exhaust conduits 6 end up. The communication of the two intakeconduits 4, 5 with the combustion chamber 2 is controlled by two intakevalves 7, of the conventional mushroom type, each comprising a stem 8slidably mounted in the body of the head 1.

Each valve 7 is returned towards the closed position by springs 9interposed between an inner surface of the head 1 and an end retainingcap 10 of the valve. The communication of the two exhaust conduits 6with the combustion chamber is controlled by two valves 70, also of theconventional type, to which springs 9 for return towards the closedposition are associated.

The opening of each intake valve 7 is controlled, as describedhereinafter, by a camshaft 11 mounted rotatably around an axis 12 withinsupports of the head 1, and comprising a plurality of cams 14 foractuating the intake valves 7. Each cam 14 which controls an intakevalve 7 cooperates with the plate 15 of a tappet 16 slidably mountedalong an axis 17 which, in the case of the example illustrated in thementioned prior art document, is substantially directed at 90° withrespect to the axis of the valve 7. The plate 15 is returned against thecam 14 by a spring associated thereto. The tappet 16 constitutes apumping piston slidably mounted within a bushing 18 carried by a body19, or “brick” of a preassembled unit 20, incorporating all electricaland hydraulic devices associated to the actuation of the intake valves,according to the description outlined hereinafter.

The pumping piston 16 is capable of transmitting a thrust to the stem 8of the valve 7, so as to cause the opening of the latter against theaction of the elastic means 9, by means of pressurised fluid (preferablyoil coming from the engine lubrication circuit) present in a pressurechamber C to which the pumping piston 16 is faced, and by means of apiston 21 slidably mounted in a cylindrical body constituted by abushing 22 also carried by the body 19 of the sub-unit 20.

Still in the known solution described in FIG. 1, the pressurised fluidchamber C associated to each intake valve 7 can be placed incommunication with an exhaust channel 23 through a solenoid valve 24.The solenoid valve 24, which can be of any known type adapted to thefunction illustrated herein, is controlled by electronic control means,indicated schematically with 25, as a function of the signal Sindicating the operating parameters of the engine, such as the positionof the accelerator and the number of engine revolutions.

When the solenoid valve 24 is open, the chamber C enters incommunication with the channel 23, hence the pressurised fluid presentin the chamber C flows into such channel and thus obtaining thedecoupling of the cam 14 and the decoupling of the respective tappet 16from the intake valve 7, which thus quickly returns to the closingposition thereof under the action of the return springs 9. Thus,controlling the communication between the chamber C and the exhaustchannel 23, allows varying the opening time and the travel of eachintake valve 7 at will.

The exhaust channels 23 of the various solenoid valves 24 end up in thesame longitudinal channel 26 communicating with pressure accumulators27, only one of which can be observed in FIG. 1.

All tappets 16 with the associated bushings 18, the pistons 21 with theassociated bushings 22, the solenoid valves 24 and the respectivechannels 23, 26 are carried by and obtained from the abovementioned body19 of the preassembled unit 20, to the advantage of an engine that isquick and easy to assemble.

The exhaust valves 70 associated to each cylinder are controlled, in theembodiment illustrated in FIG. 1, conventionally, by a respectivecamshaft 28, through respective tappets 29, even though, in the case ofthe mentioned prior art document, an application of the hydraulicactuation system also controlling exhaust valves cannot be excludedgenerally.

Still with reference to FIG. 1, the variable volume chamber definedwithin the bushing 22 and facing the piston 21 (which is illustrated inthe minimum volume condition thereof in FIG. 1, piston 21 being in theupper end stop position thereof) communicates with the pressurised fluidchamber C through an opening 30 obtained in an end wall of the bushing22. Such opening 30 is engaged by an end nose 31 of the piston 21 so asto provide a hydraulic braking of the movement of the valve 7 in theclosing phase, when the valve is close to the closing position, in thatthe oil present in the variable volume chamber is forced to flow intothe pressurised fluid chamber C passing through the clearance presentbetween the end nose 31 and the opening wall 30 engaged thereby. Besidesthe communication constituted by the opening 30, the pressurised fluidchamber C and the variable volume chamber of the piston 21 communicatewith respect to each other through internal passages obtained in thebody of the piston 21 and controlled by a check valve 32 which allowsthe passage of fluid only from the pressurized chamber C to the variablevolume chamber of the piston 21.

During the normal operation of the known engine illustrated in FIG. 1,when the solenoid valve 24 excludes the communication of the pressurisedfluid chamber C with the exhaust channel 23, the oil present in suchchamber transmits the movement of the pumping piston 16, imparted by thecam 14, to the piston 21 which controls the opening of the valve 7. Inthe initial phase of the opening movement of the valve, the fluid comingfrom the chamber C reaches the variable volume chamber of the piston 21passing through the check valve 32 and further passages which place theinternal cavity of the piston 21, which is tubular-shaped, incommunication with the variable volume chamber. After a firstdisplacement of the piston 21, the nose 31 exits from the opening 30,hence the fluid coming from the chamber C may pass directly into thevariable volume chamber through the opening 30, now free.

In the reverse movement for closing the valve, as previously mentioned,during the final phase, the nose 31 enters into the opening 30 causingthe hydraulic braking of the valve, so as to avoid impacts of the bodyof the valve against the seat thereof, for example after an opening ofthe solenoid valve 24 which causes the immediate return of the valve 7to the closed position

In the described system, when the solenoid valve 24 is enabled, thevalve of the engine follows the movement of the cam (full lift). Anearly closing of the valve can be obtained by disabling (opening) thesolenoid valve 24, thus emptying the hydraulic chamber and obtain theclosing of the valve of the engine under the action of the respectivereturn springs. Analogously, a delayed opening of the valve can beobtained by delaying the opening of the solenoid valve, while thecombination of a delayed opening with an early opening of the valve canbe obtained by enabling and disabling the solenoid valve during thethrust of the relative cam. According to an alternative strategy, incompliance with the teachings of the patent application EP 1 726 790 A1of the applicant, each intake valve can be controlled in “multi-lift”mode i.e. according to two or more repeated opening and closing“sub-cycles”. In each sub-cycle, the intake valve opens and then closescompletely. The electronic control unit is thus capable of obtaining avariation of the opening instant and/or the closing instant and/or thelift instant of the intake valve, as a function of one or more engineoperative parameters. This allows obtaining the maximum efficiency ofthe engine, and lower consumption of fuel, under any condition ofoperation.

In FIGS. 2-12, the common parts or those corresponding to those of FIG.1 are indicated using the same reference number.

With reference to FIG. 2, a body 50 for supporting the camshaft 11—inwhich the seats for supporting the rotation of the shaft 11, on whichthe latter is held by means of caps 51 fastened on the body 50—ismounted on the cylinder head 1. the illustrated example refers to thecase of a four-cylinder diesel engine. However, the invention is alsoapplicable to a controlled ignition engine and with any number ofcylinders.

In the case of the solution illustrated in FIG. 2, the pre-assembledunit for the variable actuation of the intake valves of the engine isconstituted by four separate sub-units 20A, 20B, 20C, 20D, eachcomprising a respective support independent body or “brick”,respectively indicated with 19A, 19B, 19C, 19D.

As observable in FIG. 3A, the body 19A of the sub-unit 20A, andanalogously each of the other bodies 19B, 19C, 19D of the sub-units 20B,20C, 20D carries all the devices intended to allow actuating the intakevalves of the respective engine cylinder. In particular, with referenceto the sub-unit 20A, the sub-unit carries the pumping cylinder 18 whosestem is actuated by a respective cam 14 by means of a rocker arm lever52, articulated in 53 to the support body 19A and carrying a roller 54for the engagement of the cam 14. Furthermore, the support body 19A ofthe sub-unit 20A carries the two hydraulic actuators 22 respectivelyassociated to two intake valves of the respective engine cylinder.Furthermore, the body 19A carries the body of the solenoid valve 24,which simply rests within a seat arranged in the body 19A and it islocked by means of a locking plate 52 fixed by means of screws to thebody 19A. Obviously all ducts required for the hydraulic connection ofthe system for variable actuation of the valves are obtained within thebody 19A. Lastly, an upper cavity of the body 19A (indicated with 56 inFIG. 3B) is closed by means of a cover 570 fastened on the body 19A.

What is indicated above with reference to the unit 20A obviously alsoapplies for the sub-units 20B,20C and 20D.

The illustrated example, as mentioned, refers to the case of a dieselengine. FIG. 2 shows one of the injectors associated to the enginecylinders, indicated with the reference I. Each injector I is mounted inthe cylinder head through a cup-shaped casing 57, illustrated more indetail hereinafter and which is made in a single piece with therespective support body 19A of the respective sub-unit 20A.

The unit for variable actuation of the intake valves of the engine,constituted by the plurality of sub-units 20A-D is closed at the upperpart by a cover 58 with the interposition of a sealing gasket 60.

In the illustrated example, the sealing gasket 60 is received in acorresponding peripheral groove of the cover 58 (see FIG. 7) andrespectively provides sealing on the bodies 19A-D and on the body 50 forsupporting the camshaft.

However, it should be observed that the architecture of the headdescribed above is provided purely by way of non-limiting example. Forexample, the body 50 for supporting the camshaft could be made in asingle piece with the cylinder head, or it could be made in severalpieces respectively integrated in the support bodies of the sub-units20A-D.

In the case of the solution of FIG. 2, the sealing gasket 60 has a mainportion contained in a general base plane of the cover 58, and aplurality of portions 61A-D arranged longitudinally adjacent to eachother along one side of the head and associated respectively to thevarious support bodies 19A-D of the sub-units 20A-D. Each of saidportions 61A-D has two lateral portions 62 which extend in planesparallel and orthogonal to the abovementioned general base plane, and acentral portion 63 which extends in a parallel plane with respect to theabovementioned general base plane and raised with respect thereto. Inparticular, as observable in FIG. 7, each of the lateral portions 62 hasa rectilinear main section which—at the end—extends in two briefsections one respectively contained in the general base plane of thecover and the other in the plane in which the central portions 63extend.

Due to the abovementioned arrangement, the sealing of the fluid of thesystem for variable actuation of the intake valves (typically enginelubrication oil) at each of the sub-units 20A-20D is ideally guaranteed,even in the area that separates each sub-unit 20 from the one adjacentthereto (also see FIG. 8A).

As indicated above, a problem observed in an engine of this type lies inguaranteeing the sealing around each injector I, regardless of thepresence of the actuators 22 of the intake valves arranged closelyadjacent to the injector. For such purpose, as previously described,each injector is surrounded by a cup-shaped casing 57, shaped extendedhorizontally, obtained in a single piece with the respective body 19A-Dof the respective sub-unit 20A-D. The cup-shaped casing 57 defines anupper peripheral edge for the engagement of a respective sealing gasket64 arranged within a respective groove in the lower surface of the cover58 (FIG. 7). The plane of the upper edge of the cup-shaped casing 57 isparallel but raised with respect to the general base plane of the cover,so that the casing 57 can have the required dimension, without the riskof interference with the actuators 22 associated to the intake valves ofthe respective cylinder (see FIG. 3A). Actually, should the sealinggaskets 64 of the casings surrounding the injectors I be in the generalbase plane of the cover, there would be no sufficient room to receivethem in the area comprised between the body of the injector and the bodyof the aforementioned actuators 22. Therefore, the arrangement describedabove allows guaranteeing an ideal sealing also at each injector I.

Each injector is locked in the seat thereof in the cylinder head (seeFIGS. 4, 5) by means of a bracket 640 which has an end resting on asupport (in the example the head of a screw 65 which is used for fixingthe body 50 on the cylinder head). The opposite end of the bracket 640is fork-shaped, with two branches 66 which are engaged on two shouldersof the body of the injector. The bracket 640 is pressed in position bymeans of a screw 67 which engages the cylinder head. The screw 67traverses the cover with the interposition of sealing rings and it isengaged at the upper end thereof by a nut 68 which presses—fromabove—the intermediate portion of the bracket 640, to lock the injectorI in the seat thereof.

FIGS. 9-12 refer to a different embodiment of the invention, also inthis case for a diesel engine. Also such embodiment has thecharacteristic of having cup-shaped casings 57 associated to theinjectors of the various engine cylinders and defining an upper sealingedge contained in a parallel plane and raised with respect to thegeneral base plane of the cover (not shown in FIGS. 9-12). Suchembodiment does not provide for separate sub-units for the system forvariable actuation of the intake valves, but two single longitudinalbodies 70, 71 mounted on the body 50 carrying the camshaft 11. The firstlongitudinal body 70 closes—at the upper part—the seat for rotatablysupporting the camshaft 11 and integrates the cup-shaped casings 57associated to the various injectors I.

The body 70, in a different embodiment, can be subdivided into a numberof sub-units equivalent to the number of the injectors (i.e. of thecylinders) each integrating the cup-shaped casing 57 and serving or notserving the function of closing the camshaft at the upper part.

The second longitudinal unit 71 integrates the components of variableactuation of the intake valves of the various cylinders, with therelative solenoid valves 24. Also in this case (see FIGS. 11, 12) eachinjector is locked in the seat thereof by means of a bracket 65 (FIG.12) with fork-shaped end, whose branches 66 engage correspondingshoulders provided for in the body of the injector I. Also in this caseeach bracket 640 has an end resting on the head of a screw 65 and it ispressed in position by a nut 68 engaged on the upper end of a screw 67which is fastened in the cylinder head and passes through the body 50,the body 70 and the bracket 640.

Obviously, without prejudice to the principle of the invention, theconstruction details and the embodiments may widely vary with respect towhat has been described and illustrated purely by way of example,without departing from the scope of protection of the present invention.

1. Multi-cylinder internal combustion engine, comprising, for each cylinder: a fuel injector, at least one intake valve and at least one exhaust valve for each cylinder, each provided with respective return spring means which push the valve towards a closed position, for controlling respective intake and exhaust conduits, at least one camshaft, for actuating the intake valves of the engine cylinders by means of respective tappets, wherein each intake valve is controlled by the respective tappet, against the action of the aforementioned return spring means, by interposing hydraulic means including a pressurised fluid chamber and a hydraulic actuator associated to each intake valve and connected to said pressurised fluid chamber, said pressurised fluid chamber being adapted to be connected by means of a solenoid valve with an exhaust channel with the aim of decoupling the intake valve from the respective tappet and causing the quick closure of the valve due to the respective return spring means, said hydraulic actuator further being provided with hydraulic braking means for slowing the final phase of the travel for closing the intake valve controlled thereby when the pressure chamber is connected to the exhaust channel, electronic control means for controlling each solenoid valve so as to vary the time and/or the opening travel of the respective intake valve as a function of one or more engine operative parameters, wherein the hydraulic means for controlling the intake valves of the engine and the solenoid valves associated thereto are part of a preassembled unit mounted on the cylinder head of the engine, characterised in that the fuel injector associated to each engine cylinder is surrounded by a sealing casing which is part of a support body mounted on the engine cylinder head and which defines a sealing peripheral edge cooperating with a sealing cover which is mounted on said cylinder head, said cover having a general base plane sealingly mounted on said cylinder head, and in that said sealing peripheral edge of each sealing casing is arranged in a plane parallel and raised with respect to the general base plane of said cover.
 2. Engine according to claim 1, wherein said preassembled unit is formed by a plurality of separate sub-units respectively associated to the engine cylinders and each having an independent support body, mounted on the cylinder head and carrying said hydraulic means and said solenoid valve for controlling the intake valves of the respective cylinder, and in that the sealing casing of each injector is part of the support body of the sub-unit associated to the respective cylinder.
 3. Engine according to claim 1, wherein the sealing casing of each injector is part of a single support body common for all the engine cylinders and which is mounted on the cylinder head so as to close at the upper part the seat in which said camshaft is received.
 4. Engine according to claim 3, wherein the common support is mounted on the cylinder head with the interposition of a support surmounting the head and defining the seat in which said camshaft is received.
 5. Engine according to claim 2, wherein the abovementioned cover covers said pre-assembled unit and it has a base peripheral edge having a perimeter groove for mounting a sealing gasket, and wherein said sealing gasket has a main portion extending in a general base plane of the cover and respective portions associated to said sub-units and projecting from said general plane, in positions arranged longitudinally adjacent to each other on one side of the cylinder head and each having a three-dimensional development, with two lateral parts contained in two planes substantially parallel to each other and orthogonal to said general plane and a central part contained in a parallel plane and spaced from said base plane.
 6. Engine according to claim 1, wherein each injector is locked on the cylinder head by means of a bracket which has an end resting on a support fixed to the cylinder head and the opposite fork-shaped end, with two branches which are engaged on two shoulders of the body of the injector, the intermediate portion of said bracket being pressed in position by means of a screw which engages the cylinder head. 